<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        div{
            margin: 30px;
            border: 5px solid #000;
            padding: 20px;
            /* width: 200px;
            height: 100px; */
            /* box-sizing: border-box; IE盒模型 */
            /* box-sizing: content-box;    标准盒模型 */
        }
    </style>
</head>
<body>
    <div id="wrap" style="width: 200px; height: 100px;">hello world</div>

    <script>
        let dom = document.getElementById('wrap')
        // dom.style.width = 300 + 'px'
        // console.log(dom.style.width);

        // dom.offsetWidth = 300 + 'px' //不能设置
        // console.log(dom.offsetWidth);    //能获取

        // dom.getBoundingClientRect().width = 300 +'px'    //不能设置
        // console.log(dom.getBoundingClientRect().width);  //能获取

        // window.getComputedStyle(dom).width = 300 + 'px' //不能设置
        // console.log(window.getComputedStyle(dom).width);    //能获取

        console.log(dom.currentStyle.width);    //能获取，但只支持IE
    </script>
</body>
</html>